1. Field of the Invention
This invention relates generally to optical reproducing apparatus and, more particularly, is directed to apparatus for optically reproducing audio information from a record disk.
2. Description of the Prior Art
Apparatus is known in the art for optically reproducing an information signal from a record disk during rotation of the latter. With such apparatus, a pick-up device is positioned below the record disk and projects a laser beam onto the disk. The laser beam is modulated by, for example, audio information recorded on the disk and the modulated laser beam is reflected from the underside of the disk back to the pick-up device which produces an output signal in response to the modulated laser beam and which supplies such signal to further processing circuitry for removing the audio information therefrom.
In one such apparatus, it has been proposed to detect address information also recorded on the record disk for performing a search or cueing operation so that reproduction at a desired point can be easily and quickly achieved. With such apparatus, the pick-up device is moved at a speed faster than the normal reproduction speed, while the record disk is rotated at the normal reproduction speed. Accordingly, normal reproduced sound is produced at the output of the apparatus, and address information is detected to perform the cueing operation for obtaining a desired address. Generally, the pick-up device includes a tracking servo system for causing the pick-up device to accurately trace the correct track and a focusihg servo system for focusing the laser beam through an objective lens onto and from the record disk. It is to be appreciated that, as the pick-up device is moved radially of the record disk by the tracking servo system, the focusing of the laser beam onto and from the disk changes. Accordingly, during such faster radial movement of the pick-up device, the objective lens thereof is moved from a first position toward a second position to maintain the focus of the laser beam onto the record disk. When the objective lens reaches a critical or limit point at the second position, it is skipped or jumped back to the first position to maintain the focus of the laser beam. In this manner, only a portion of the information, both audio and address, are detected.
Thus, during the cueing or search operation, the pick-up device reproduces audio and address information from a portion of the record disk, skips over a portion and repeats the cycle. The address information reproduced by the pick-up device is compared with desired address information to control the tracking servo system so that the pick-up device is moved to the desired address point. However, with such apparatus, the maximum time required for the cueing or search operation becomes relatively long, for example, of the order of 13.25 seconds and the mean search time is approximately one-half of this time.